Muscle
Triceps brachii
Main muscle for straightening the elbow
High-yield
Triceps is the principal elbow extensor, assisted by anconeus. Its stretch reflex mainly reflects C7 through the radial nerve.
Overview
Three heads converge behind the arm toward the olecranon. All extend the elbow; the long head also crosses the shoulder, so it can help move the arm backward and toward the body.
Reference facts
- Origin
- Long head: infraglenoid tubercle; lateral head: posterior humerus above the radial groove; medial head: posterior humerus below it
- Insertion
- Olecranon of the ulna through the triceps tendon
- Action
- Extends the elbow; the long head also assists shoulder extension and adduction
- Innervation
- Radial nerve, C6–C8, with C7 prominent
- Blood supply
- Mainly the deep brachial artery, with ulnar collateral contributions
Clinical correlation
A radial nerve lesion at the humeral groove often spares useful elbow extension because many triceps branches arise farther proximally. Wrist and finger extension can still be severely affected; the precise deficit depends on the lesion.
Frequently asked questions
What does the triceps brachii do?
Extends the elbow; the long head also assists shoulder extension and adduction.
What nerve innervates the triceps brachii?
The triceps brachii is innervated by the radial nerve, C6–C8, with C7 prominent.
Where does the triceps brachii attach?
Origin: Long head: infraglenoid tubercle; lateral head: posterior humerus above the radial groove; medial head: posterior humerus below it. Insertion: Olecranon of the ulna through the triceps tendon.
What is the blood supply of the triceps brachii?
Mainly the deep brachial artery, with ulnar collateral contributions.